When treating diabetes patients, it is a common practice to measure the glucose concentration in blood sampled from the patient, for developing a treatment plan according to the measured value. Devices currently employed for such a purpose include a lancing apparatus according to JP-A 2001-346781, which is shown in FIG. 18A.
The lancing apparatus 9 shown therein includes a lancet 91 advanceably disposed in a cylindrical portion 90 of a housing with an opening at its outer end portion. The cylindrical portion 90 includes a flange portion 93 with a small hole 92 located at a central portion, and a glucose concentration meter 94 is disposed so as to project halfway into the hole 92. The lancing apparatus 9 also includes an electric pump (not shown) which, when activated, generates a negative pressure inside the cylindrical portion 90.
When using the lancing apparatus 9, upon activating the electric pump with the end portion of the cylindrical portion 90 brought into contact with a skin Sk, to thus generate a negative pressure inside the cylindrical portion 90, the skin Sk is caused to swell upward in the cylindrical portion 90. The swelling motion of the skin Sk is blocked by the flange portion 93. The lancet 91 automatically starts to move forward when a predetermined time has passed after the electric pump is activated, thus to stick into the skin Sk, thereby causing the skin Sk to bleed. The blood that has come out of the skin Sk is sampled by the glucose concentration meter 94, with an assistance of the negative pressure facilitating the skin to bleed. Accordingly, the lancing apparatus 9 is designed to sample a sufficient amount of blood for glucose concentration measurement, with a minimal insertion depth of the lancet 91.
However, the lancing apparatus 9 has the following drawbacks, originating from the setting that the lancet 91 automatically advances toward the skin Sk after driving the electric pump for a predetermined time.
In the lancing apparatus 9, the negative pressure may not be effectively acting on the skin Sk, after driving the electric pump for a predetermined time. For example, if the cylindrical portion 90 is improperly applied to the skin Sk so as to produce a gap between the cylindrical portion 90 and the skin Sk, air intrudes into the cylindrical portion 90 and interrupts the generation of the negative pressure. Also, even though the negative pressure is generated as expected, the swelling motion of the skin Sk largely depends on softness of the skin Sk.
For such reasons, the lancing apparatus 9 may fail to cause the skin Sk to sufficiently swell as shown in FIG. 18B, when there is a gap between the cylindrical portion 90 and the skin Sk, or when the skin Sk is not soft enough. If the lancet 91 is moved forward for insertion into the skin Sk under such a state, the lancet 91 may not reach the skin Sk, or may not be inserted deeply enough to provoke sufficient bleeding.
On the other hand, when the skin Sk is soft, although the skin Sk is sufficiently raised by the negative pressure, a portion Sk1 of the skin Sk may be tightly pressed against the flange portion 93 and depressed thereby, as shown in FIG. 18C. Such pressure against the skin Sk/Sk1 may lead to insufficient bleeding from the sticking point. In addition, another portion Sk2 indicated in FIG. 18C of the skin Sk may intrude into the small hole 92 because of the negative pressure, and may even protrude upward beyond the flange portion 93. In such a case the lancet 91 is inserted too deeply into the skin Sk, which not only causes a considerable damage on the skin Sk, but also makes the patient feel an intolerable pain.